By Ed Yong – The Atlantic.
CRISPR can finally tell us which human genes are essential—and which matter specifically to cancer cells
It’s crazy to me that we still don’t know, even though it’s been almost 15 years since the first draft of the human genome was published. Partly, the problem is a technological one. The best way of working out if a gene is essential is to disable it and see what happens, and “we just didn’t have a good way of systematically manipulating genes in humans cells,” says Jason Moffat from the University of Toronto. Sure, scientists have been able to tinker with individual genes, but working through them all, and knocking them out one by one, has been nigh-on impossible.
A technique called RNA interference has come closest. When genes are activated, the instructions encoded within their DNA must first be transcribed into a related molecule called RNA. By interfering with these transcripts, scientists can stop those instructions from ever being realized. But this technique is imperfect: It often fails to silence genes entirely, and it sometimes silences the wrong gene. “That technology allowed us to uncover some of the essential genes but our confidence wasn’t super-high,” says Moffat.
Enter the revolutionary gene-editing technique called CRISPR, which was invented billions of years ago by bacteria, as part of a defense system for hacking into the genes of invading viruses. But in the last five years, scientists have repurposed it into a tool that can edit any gene at will. Unlike RNA interference, which disables the messages transcribed from genes, CRISPR alters the gene itself… read the full article.